Ionic bonding does not involve the sharing of electrons, that one is false. In ionic bonding, the metal's electrons are given to the non-metal, so that they're both like the nearest noble gas (full electron shells.) They are then drawn together because one has a negative charge (the non-metal) and one has a positive charge (the metal.)
Oxide ions have a 2+ charge: This is false, oxide ions have a 2- charge.
Electrons do have a negative charge, this is true.
Hydrogen molecule: pretty sure this is true. We know this because both atoms are non-metals.
The last one is true: a covalent bond is a shared pair of electrons between two atoms, however be aware that there can be more than one covalent bond between two molecules.
Because the Potassium ion loses an electron, the electrons come a little closer to the nucleus because they are attracted to the protons. This makes the ion smaller in radius
